1. Field of the Invention
This invention pertains generally to light emitting devices, and more particularly to structures and methods to inject electrons from a semiconductor surface, through an insulator layer, and into a layer of optoelectronic material placed on the insulator layer. Additionally, it pertains to methods of transporting emitted light to remote locations.
2. Description of the Background Art
The following publications, some of which are referred to herein using their corresponding number inside a square bracket (e.g., [1]), are incorporated herein by reference herein as background information for this application:
1. Shealy, J. R.; Macdonald, N. C.; Whittingham, Y. Xu. K. L.; Emerson, D. T.; Pitts, B. L.; “Direct band gap structures on nanometer-scale, micromachined silicon tips”, Appl. Physics Letters, Vol. 70, (no. 25), AIP, June 1997, p. 3458-3460.
2. Ellis, R. K., Wegener, H. A. R., and Caywood, J. M.; “Electron tunneling in non-planar floating gate memory structure”, IDEM, 1982, pp. 749-752.
3. Prickett, B. L., Caywood, J. M., Ellis, R. K.; “Trapping in tunnel oxides grown on textured polysilicon”, 21st annual Proceedings on Reliability Physics, 1983, pp. 114-117.
4. Wegener, H. A. R., Guterman, D. C.; “The prediction of textured poly floating gate memory endurance”, 23rd annual Proceedings on Reliability Physics, 1985, pp. 11-17.
5. Sun, Y., Giebink, N. C., Kanno, H., Ma, B., Thompson, M. E., Forrest, S. R.; “Management of singlet and triplet excitons for efficient white organic light-emitting devices”, Nature, Vol. 440, pp. 918-912, Apr. 13, 2006.
While silicon has been a wonderful material for integrated electronic as well as micromechanical structures, silicon is not a material suitable for light emission. Light emission to and from integrated structures is increasingly important as device integration becomes denser and more complex. Typically, light emitting structures are formed in materials known as Light Emitting Materials (LEM) that include direct semiconductors that are found in compound II-V and II-VI, as well as ternary and quaternary materials known in the art and a variety of luminescent materials and organic light emitting materials (OLED). It should be appreciated that certain of these LEMs including the direct semiconductors may be selectively doped and otherwise altered in composition so as to enhance the probability of radiative recombination in certain areas of the LEM as is known in the art. Light emitted from LEMs may be transported from the point of emission to other locations by optical wave guiding structures derived from the “Integrated Circuit back end” metal and insulating layers found in integrated circuit structures. The emitted light can also be directed into portions of the lid or other portions of the package where the light is again guided to desired locations on the emitting or other chips or structures as desired.
Single crystal direct semiconductor integrated circuits have proven to be more difficult and expensive to form into integrated structures, so silicon integrated circuits are the technology of choice. Attempts to integrate light emission with the silicon technology have not met with a great deal of success. While silicon emission has been reported in porous silicon and it is suggested that quantum dots of silicon may be able to emit light, neither of these possibilities appears to be a practical solution at this time. It has also been reported that selectively deposited polycrystalline direct compound semiconductors placed on silicon tip arrays formed in single crystal silicon result in light emission [1]. The light emission is caused by the emission of electrons from the from the high electric field areas of the tips into the deposited direct materials which subsequently emit the light by direct recombination. This technique, however, requires difficult and expensive tips to be formed and does not combine well with the silicon integrated circuit technology.